Rate-based multivariable control with stability assurance

Abstract

Method, system and computer executable instructions for controlling a process.

What is claimed is: 
     
       1. A method of process control of a unit operation within an industrial process comprising:
 collecting data sets for a multivariable process having an initial base layer Direct Control Variable value and multiple corresponding initial Indirect Control Variable values, a rate-time value and a move series value; 
 receiving a target Indirect Control Variable value for each Indirect Control Variable; 
 determining whether a change in Direct Control Variable value is needed; 
 if needed, implementing a move series to the Direct Control Variable value; 
 calculating a rate-of-change of each Indirect Control Variable value and an estimated time needed to reach the target indirect Control Variable value for each Indirect Control Variable; 
 comparing the estimated times needed to reach each target Indirect Control Variable value with the rate-time; 
 discontinuing the Direct Control Variable move series when the time needed to reach one of the Indirect Control Variable value is less than a predetermined percentage of the rate-time value; 
 wherein the method does not utilize model-based control; and 
 wherein the method controls one or more Direct Control Variable selected from the group consisting of: a flow controller, a temperature controller, a level controller, a pressure controller, and a stream property controller; 
 wherein the one or more Direct Control Variable is an element of a unit operation within an industrial process, the industrial process selected from the group consisting of: mineral refining, oil refining, gas processing, natural gas liquids fractionation, chemical production, petrochemical production, fossil fueled power generation, nuclear power generation, food processing, and pharmaceutical production. 
 
     
     
       2. The method of  claim 1 , further comprising checking process stability. 
     
     
       3. The method of  claim 2 , wherein if an unstable condition within the process is detected the move series is temporarily halted until stability is achieved. 
     
     
       4. The method of  claim 1 , wherein the method does not utilize non-linear optimization. 
     
     
       5. The method of  claim 1 , wherein the method is not affected by changes in process gain. 
     
     
       6. The method of  claim 1 , wherein the method is not affected by changes in move size. 
     
     
       7. The method of  claim 1 , wherein the method is not affected by complex process interaction dynamics. 
     
     
       8. The method of  claim 1 , further comprising:
 assigning a control priority to each Indirect Control Variable; and 
 discontinuing the Direct Control Variable move series when the time needed to reach the Indirect Control Variable value with highest control priority is less than a predetermined percentage of the rate-time value. 
 
     
     
       9. The method of  claim 1 , further comprising:
 discontinuing the Direct Control Variable move series if the Direct Control Variable move series can not improve one Indirect Control Variable value without worsening a different Indirect Control Variable value. 
 
     
     
       10. A method of process control of a unit operation within an industrial process comprising:
 collecting data sets for a multivariable process having multiple initial Direct Control Variable values and a corresponding initial Indirect Control Variable value, a rate-time value and a move series value; 
 receiving a target Indirect Control Variable value; 
 determining whether a change in a Direct Control Variable value is needed; 
 assigning a control priority to each Direct Control Variable; 
 if needed, implementing a move series to the Direct Control Variable value having the highest control priority; 
 calculating a rate-of-change of the Indirect Control Variable value and an estimated time needed to reach the target Indirect Control Variable value; 
 discontinuing the Direct Control Variable move series when the time needed to reach the Indirect Control Variable value is less than a predetermined percentage of the rate-time value; 
 wherein the method does not utilize model-based control; and 
 wherein the method controls one or more Direct Control Variable selected from the group consisting of: a flow controller, a temperature controller, a level controller, a pressure controller, and a stream property controller; 
 wherein the one or more Direct Control Variable is an element of a unit operation within an industrial process, the industrial process selected from the group consisting of: mineral refining, oil refining, gas processing, natural gas liquids fractionation, chemical production, petrochemical production, fossil fueled power generation, nuclear power generation, food processing, and pharmaceutical production. 
 
     
     
       11. The method of  claim 10 , further comprising checking process stability. 
     
     
       12. The method of  claim 11 , wherein if an unstable condition within the process is detected the move series is temporarily halted until stability is achieved. 
     
     
       13. The method of  claim 10 , wherein the method does not utilize non-linear optimization. 
     
     
       14. The method of  claim 10 , wherein the method is not affected by changes in process gain. 
     
     
       15. The method of  claim 10 , wherein the method is not affected by changes in move size. 
     
     
       16. The method of  claim 10 , wherein the method is not affected by complex process interaction dynamics. 
     
     
       17. The method of  claim 10 , further comprising:
 if the Direct Control Variable having the move series is unable to control the Indirect Control Variable then the move series of that Direct Control Variable value will cease; and 
 if needed, implementing a move series to the Direct Control Variable value having the next highest control priority. 
 
     
     
       18. A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform the method of  claim 1  and control a unit operation within an industrial process. 
     
     
       19. A non-transitory computer-readable medium storing instructions that, when executed by a processor, cause the processor to perform the method of  claim 10  and control a unit operation within an industrial process. 
     
     
       20. A system to control a unit operation within an industrial process comprising:
 at least one processor; 
 at least one memory coupled to the at least one processor and storing computer executable instructions for a model-less multivariable process control, the computer executable instructions comprising instructions for the method of  claim 1 ; 
 wherein the executable instructions control one or more Direct Control Variable selected from the group consisting of: a flow controller, a temperature controller a level controller, a pressure controller, and a stream property controller; 
 wherein the one or more Direct Control Variable is an element of a unit operation within an industrial process, the industrial process selected from the group consisting of: mineral refining, oil refining, as processing natural gas liquids fractionation, chemical production, petrochemical production, fossil fueled power generation, nuclear power generation, food processing, and pharmaceutical production. 
 
     
     
       21. A system to control a unit operation within an industrial process comprising:
 at least one processor; 
 at least one memory coupled to the at least one processor and storing computer executable instructions for a model-less multivariable process control, the computer executable instructions comprising instructions for the method of  claim 10 ; 
 wherein the executable instructions control one or more Direct Control Variable selected from the group consisting of: a flow controller, a temperature controller, a level controller, a pressure controller, and a stream property controller; 
 wherein the one or more Direct Control Variable is an element of a unit operation within an industrial process, the industrial process selected from the group consisting of: mineral refining, oil refining, gas processing, natural gas liquids fractionation, chemical production, petrochemical production, fossil fueled power generation, nuclear power generation, food processing, and pharmaceutical production.